RDH法和常规KP法蒸煮过程中蒸煮液组成的变化及对比

Comparison of Characteristics of Cooking Liquor during RDH Pulping and Conventional Batch Kraft Pulping

对RDH(快速置换加热 )硫酸盐法和常规KP法蒸煮过程中蒸煮液组成的变化规律进行了研究和对比。结果表明 ,在RDH硫酸盐法和常规KP法蒸煮过程中 ,蒸煮液中NaOH和Na2 S含量均下降 ,但蒸煮液硫化度升高。与常规KP法相比 ,在整个脱木素反应过程中 ,RDH蒸煮液的有效碱浓度分布较均匀 ,蒸煮液中Na2 S浓度较高 ,尤其在大量脱木素的开始阶段 (此时蒸煮液中Na2 S浓度是常规KP法蒸煮时的 2 .88倍 ) ,因而RDH法蒸煮能够深度脱除木素。与常规KP法蒸煮废液相比 ,在废液粘度相近的条件下 ,RDH法蒸煮废液有较高的固含量 ,有利于黑液的碱回收。在RDH硫酸盐法蒸煮经过一次完整的循环置换蒸煮周期后 ,温黑液槽和热黑液槽内的黑液组成基本保持稳定 ,可为后续进行的连续置换加热蒸煮提供良好的前提条件。

The change of characteristics of cooking liquor during conventional batch kraft pulping and rapid-displacement-heating (RDH) kraft pulping was studied and compared. The results showed that NaOH content and Na2S content of cooking liquor were decreased, but the sulfidity was increased either in RDH pulping or conventional kraft pulping. Compared to conventional kraft pulping, RDH pulping could extent delignification due to relative uniform effective alkali concentration and higher sodium sulfide concentration during pulping, especially at the beginning of the bulk delignification phase of the pulping, sodium sulfide concentration of RDH cooking liquor was 2.88 times higher than that of conventional kraft cooking liquor when the same white liquor with a 30% sulfidity was used. The black liquor from the RDH pulping process had higher solid content at similar viscosity value compared to the conventional batch process, it was favorable to chemical recovery of black liquor. After a RDH cooking cycle was completed, characteristics of the liquor in warm black liquor tank and hot black liquor tank were basically stable.